US President Donald Trump has reaffirmed his "confidence" in North Korean leader Kim Jong-un, tweeting an approving snicker at his recent insult of Joe Biden and brushing off concerns over Pyongyang's short-range missile tests.

Donald Trump took to Twitter on Saturday to rekindle his somewhat stale bromance with Kim, hanging in the balance after their summit in Vietnam in February faltered and was further threatened by the recent seizure of a North Korean cargo ship by the US.

Trump, on a state visit to Japan, which eyes hosting its own summit with North Korea, defied hawkish National Security Advisor John Bolton, tweeting dismissively about "some small weapons" fired by Pyongyang "which disturbed some of my people, and others, but not me."

"I have confidence that Chairman Kim will keep his promise to me," Trump tweeted.

Trump has previouslydownplayedthe fact that Pyongyang ended its self-imposed moratorium on missile tests by test-firing several short-range ballistic missiles on May 4 and 10.

While the launches left the US president unfazed, they did not sit well with his entourage, namely Bolton, who accused Pyongyang of violating UN Security Council resolutions.

"Banning launches using ballistic technology is equal to telling us to give up our right to self defence. Even in the US, Bolton is well-known as a war fanatic. Such a human defect must go away as soon as possible."

Next, Trump complimented Kim's recent insult of his most likely 2020 Democratic challenger, former Vice President Joe Biden. A connoisseur of petty name-calling himself, he apparently felt inspired by the Korean State News Agency, which labeled Biden a "fool of low IQ," to come up with a new nickname for him (while not actually spelling his name correctly).

Trump didn't elaborate on the "signal" part, though it does seem in keeping with previous flirtatious statements. On several occasions, Trump has professed his affections, talking about "beautiful letters" from the North Korean leader, and once even saying that he "fell in love" with Kim.

The feelings appear to be unrequited. At least publicly, Pyongyang has had few nice words for Trump's administration, warning the US on Friday that it would not resume the stalled denulcearization talks until Washington drops its "impossible demands."

"He [Kim] knows that with nuclear... only bad can happen. He is a very smart man, he gets it well," Trump remarked, stressing that North Korea has "tremendous economic potential."

At the same press conference, he said regarding Iran:

"We're not looking for regime change, we're looking for no nuclear weapons.The prime minister's [Abe] already spoken to me about that, and I do believe that Iran would like to talk. And if they'd like to talk, we'd like to talk also.We'll see what happens... nobody wants to see terrible things happen, especially me. "

The most successful tyranny is not the one that uses force to assure uniformity but the one that removes the awareness of other possibilities, that makes it seem inconceivable that other ways are viable, that removes the sense that there is an outside.